In semiconductor arts, structures are obtained on semiconductor wafers or substrates to form a variety of electronic components on the wafer, such as transistors. The wafers are processed, for example, by well-known lithography and etching steps in chambers. The wafer is usually supported by a chuck. Such a process chamber with chuck is illustrated, for example, in U.S. Pat. No. 5,904,800 to Mautz titled "Semiconductor wafer processing chamber . . . ". Two types of lithography chucks currently exist: pin chucks (also referred to as "bed-of-nails") and ring chucks.
U.S. Pat. No. 5,197,089 to Baker titled "Pin chuck for lithography system" illustrates a wafer chuck that supports the wafer by a plurality of closely spaced extensions, each having a top that is on the same plane as the top of the other extensions. The space between the extensions is evacuated (vacuum) and the pressure difference holds the wafer in place.
U.S. Pat. No. 4,506,184 to Sidall titled "Deformable chuck driven by piezoelectric means" illustrates a deformable vacuum pin chuck having a thin silicon chuck for supporting a semiconductor wafer during lithographic processing and a number of piezoelectric transducers for selectively deforming the chuck.
However, lithography chucks are susceptible to wafer backside contamination that causes pattern replication errors or other unwanted non-flatness effects that could cause undesirable rework. The present invention seeks to provide an improved chuck as well as a method that mitigate or avoid disadvantages and limitations of the prior art.